CN110361314B - Sealing method and device suitable for large-scale three-way loading permeameter - Google Patents

Abstract

Sealing method and device suitable for large-scale three-way loading permeameter: return all push plates of the instrument to their original positions; glue a back-shaped rubber plate around the water inlet hole of the water inlet push plate and around the water outlet hole of the water outlet plate, Place a rubber sheet inside the test chamber to cover the front, bottom and rear sides of the instrument; put a custom-made water bladder, place geotextiles and looped rubber sheets in order on the water inlet side inside the bladder, and place looped rubber on the water outlet side Fill the water bladder from the top; cover with a layer of rubber sheet; add a whole sealing strip in the sealing groove reserved at the top; add the upper cover of the instrument; apply a certain pressure to each push plate; Water is saturated and then the corresponding penetration test is carried out. The invention solves the problems of seepage around and side wall effect existing in the model test of the large-scale three-way loading permeameter, ensures that the seepage water flows out from the water inlet hole after entering through the whole soil body, and ensures the rationality of the test path. It also ensures the tightness of the entire instrument cavity under high water pressure.

Description

Sealing method and device suitable for large-scale three-way loading permeameter

technical field

The invention relates to a seepage model test sealing system under the action of high stress, and belongs to the technical field of experimental theory. It is especially suitable for the overall sealing of the large-scale true triaxial permeameter when carrying out high-stress and high-head seepage model test research to ensure the rationality of the permeation path and reduce the side wall effect.

Background technique

With the relocation of the national resource construction and development focus, a large number of water resources in the central and western regions have gradually been put on the development and utilization schedule. A series of 200m-level and even 300m-level ultra-high earth-rock dams have been established for investigation or construction. The original conventional triaxial seepage meter and flume seepage meter , it has been unable to meet the needs of the research on the seepage mechanism and anti-seepage measures of extra-high earth-rockfill dams. It is necessary to develop a large-scale three-way loading permeameter to simulate the seepage characteristics of real soil units under the action of high stress and high water head.

For a large three-way loading infiltration instrument, the stress is generally applied directly on the soil through the push plate. With the movement of the push plate, a certain cavity will be formed between the back side of the push plate and the side wall of the instrument. Since the push plate can slide freely, if there is no specific water-stop sealing treatment inside the large-scale three-way loading permeameter, water can flow into the cavity through the gap between the push plate and the side wall, thereby affecting the penetration test results; in addition, the soil sample and the side wall are directly Due to the side wall effect, the contact can easily form a piping channel at the side wall, which greatly reduces the test results and affects the test reliability. At the same time, when the permeability test of high water pressure is carried out, due to the large water pressure inside the test instrument, if the instrument is separated, water can easily escape from the connection of the instrument, such as the gap between the upper cover and the lower instrument body. Dangerous if sprayed.

SUMMARY OF THE INVENTION

Based on the above considerations, in order to ensure that the seepage path is consistent with the actual seepage field of the dam body to be studied, eliminate the seepage phenomenon of the unit penetration test and reduce the influence of the side wall effect, the present invention proposes a new sealing method and sealing The system ensures the sealing performance of the sample and the safety of the test under the action of high stress state and high water head, and can also ensure the rationality of the penetration path of the sample.

To achieve the above object, the present invention adopts the following technical solutions:

A sealing method suitable for a large-scale three-way loading permeameter, characterized in that it comprises the following steps:

Step 1: Return all push plates of the instrument to their original positions;

Step 2: Glue a rubber sheet around the inlet hole of the water inlet push plate and around the outlet hole of the water outlet plate, place a rubber sheet inside the test chamber, and the rubber sheet covers the front, lower and rear sides of the instrument ( Except for the water inlet surface, water outlet surface and top), the specific size and model of the rubber sheet is determined by the calculated peak shear strength and the allowable thickness of the rubber sheet;

Step 3: Put the customized water bag, place the geotextile and the rubber sheet on the water inlet side of the bag in order, and place the rubber sheet on the water outlet side;

Step 4: Fill the test soil sample from the top of the water bag to the water bag, and each layer of rock and soil material is layered and compacted;

Step 5: Cover the top of the filled water bladder with a layer of rubber sheet;

Step 6: Add a whole sealing strip to the sealing groove reserved at the top of the instrument, connect the two ends of the sealing strip, and fix it with glue;

Step 7: Cover the top of the instrument with the upper cover of the instrument, fix it with a hydraulic nut and apply a certain pressure. The pressure depends on the test conditions and the target stress level. Generally, the hydraulic nut can meet the requirements between the upper cover and the upper cover by adding 10~20Mpa oil pressure. The strength requirements of the connection of the instrument, and at the same time, the sealing strip is deformed and flattened under the action of high pressure and the middle gap is blocked to meet the test sealing requirements;

Step 8: Give a certain initial thrust to the push plates in each direction, so that the soil sample, water bladder, rubber plate and push plate/side wall in the test cavity are in close contact;

Step 9: Pass water to the instrument, and then perform the corresponding penetration test after saturation. Customized water bladder, the shape and size are based on the size of the specific instrument test cavity, used to wrap soil samples, the water bladder is made of TPU polyurethane software, which can be used for water storage and oil storage. The material is thickened, with certain strength and elasticity, and good tensile performance. The top opening is used for filling soil samples, and the water inlet and outlet are distributed and shaped according to the distribution and shape of the water inlet and outlet, leaving corresponding openings.

The technical solution for accomplishing the second invention task of the present application is that the sealing device used in the above method is suitable for a large-scale three-way loading permeameter, and the main body of the large-scale three-way loading permeameter is provided with an upper cover; The osmometer is provided with a push plate that acts directly on the soil. It is characterized in that a water bag is provided for wrapping the soil sample. The inner side of the cavity outside the water bag (except the water inlet and outlet surfaces) is pasted with a layer of a certain thickness. A rubber plate of a certain thickness is glued to the outside of the water inlet of the water inlet surface of the water bag according to the distribution shape of the water inlet holes, and the thickness of a circular rubber plate suitable for this sealing device is 6mm; The water outlet surface of the water bag is coated with a layer of circular rubber plate of a certain thickness according to the distribution shape of the water outlet holes, and the thickness of a circular rubber plate suitable for this sealing device is 6mm; A perforated rubber sheet with a certain thickness, a perforated rubber sheet suitable for this sealing device, has a thickness ranging from 10 to 20 mm. There is a groove on the top working platform of the main body of the large three-way loading permeameter. The groove There is a sealing strip in the middle.

In other words, the structure of the sealing device of the large-scale three-way loading permeameter of the present invention is: a custom-made water bag, the shape and size of which is based on the size of the specific instrument test cavity, used to wrap the soil sample, and the water bag is made of TPU polyurethane software, which can be used for water storage and oil storage , The material is thickened, has a certain strength and elasticity, and has good tensile properties. The top opening is used for filling soil samples, and the water inlet and outlet are distributed and shaped according to the distribution and shape of the water inlet and outlet, leaving corresponding openings.

A layer of rubber sheet with a certain thickness is attached to the inside of the cavity outside the water bag (except the water inlet and outlet surfaces), which can prevent water from entering the rear cavity of the push plate outside the water bag. In addition, during the pressurization process, the soil sample, the water bladder and the rubber sheet are in close contact, and the soil particles on the edge are embedded in the rubber sheet through the water bladder. , on the other hand, it can reduce the pore channels on the side wall and reduce the side wall effect.

For the water inlet surface, a layer of circular rubber sheet with a certain thickness is pasted outside the water inlet according to the distribution shape of the water inlet holes, and corresponding holes are also opened on the water bag for water inlet. A layer of geotextile is attached to the water bag to prevent soil particles from blocking the water inlet during the pressurization process, and a perforated rubber plate is clamped inside the geotextile, so that after axial compression, the water bag and the geotextile It will be fixed between two rubber plates to prevent the water bladder from moving and deforming greatly during the compression process to form additional pore channels.

On the water outlet surface, dip a layer of rubber sheet with a certain thickness on the water outlet plate according to the distribution shape of the water outlet holes, and corresponding holes are also opened on the water bag for water outlet, and an open-hole rubber plate is also clamped on the inside of the water bag, so that After being pressurized, it can play the role of fixing the water bag, and the rubber plate at the water outlet plate can also prevent the water outside the water bag from flowing out of the water outlet hole after being compressed with the water bag. In this way, it can be ensured that the water flowing out of the water outlet passes through the entire soil sample, which ensures the rationality of the test seepage path and is used to simulate the seepage path of the actual dam unit.

A sealing strip should be added between the upper cover of the instrument and the lower main body of the instrument to ensure the airtightness of the inside of the instrument cavity during high water pressure test. A groove is made on the top working platform of the lower instrument body, and a sealing strip is added in the middle. The sealing strip uses a circular rubber sealing strip. The diameter matches the width of the groove, which is larger than the depth of the groove and has good elasticity. , It can be waterproof, flame retardant, acid and alkali resistance, oil resistance, insulation and aging resistance, and has good tensile properties. At the interface, there is a certain length at both ends, which is cut in half with the horizontal axis as the boundary, leaving an upper half on one side and a lower half on one end, which are fixed together with glue. After the sealing strip is installed, add the upper cover of the instrument, and press and fix it with a hydraulic nut. At this time, the rubber strip is compressed and deformed, which will completely block the gap between the groove and the upper cover, and play a good waterproof sealing effect.

Beneficial effects of the present invention:

The invention designs an instrument sealing method and device suitable for high stress and high water pressure for a large-scale three-way loading permeameter, and aims to solve the problems of seepage around and side wall effect existing in the model test of a large-scale three-way loading permeameter, It is ensured that the seepage water flows out from the water inlet hole and passes through the entire soil body, so as to ensure the rationality of the test path. On the other hand, it also ensures the tightness of the entire instrument cavity under high water pressure, effectively meeting the needs of seepage research under high pressure conditions.

In the self-developed large-scale three-way loading permeameter, a comparative test of whether to add this set of penetration sealing methods was carried out. The test material used sand and gravel material. The two groups of tests used the same sand and gravel material and the same initial dry density. The horizontal direction penetration test was carried out under the compressive stress state of 1.55Mpa, 3.1Mpa, 4.65Mpa and 6.2Mpa. The test results are shown in Figure 5. It can be seen from Fig. 5 that the permeability coefficient basically does not change with the increase of the stress level when the penetration sealing method is not used, and the permeability coefficient remains at about 1×10 ^-4 cm/s. In other words, the compression reduction of the sample pores during the test has little effect on the permeability coefficient, which is contrary to the research results and the actual situation. After the porosimeter was embedded on the back side of the push plate, it was found that during the penetration test, the water basically infiltrated from the back side of the push plate rather than along the interior of the soil sample. Therefore, the penetration test without this penetration sealing method does not meet the test requirements, and the test results have great problems; after the sealing method in this paper is adopted, the seepage water can only pass through the pore channels inside the soil body in the bag. At the same time, it can be seen from Fig. 5 that the permeability coefficient decreases with the increase of the stress level. A large number of studies have pointed out that the greater the stress on the sample during the test, the smaller the pores and the smaller the permeability coefficient. The test results are consistent with this law; and as the stress increases, the permeability coefficient decreases from 10 ^-4 to 10 ^-5 cm/s, the penetration test results obtained after using this penetration sealing method are more reliable.

Description of drawings

The patent of the present invention will be further described below in conjunction with the accompanying drawings and implementation cases:

Fig. 1 is the overall structure schematic diagram of the present invention;

Figure 2-1 and Figure 2-2 are schematic diagrams of the structure of the water inlet surface of the present invention;

Fig. 3 is the structure schematic diagram of the water outlet of the present invention;

FIG. 4 is a schematic diagram of the interface at the connection of the upper rubber strip of the present invention.

Figure 5 is a comparison chart of the penetration test results whether this sealing method is adopted.

Detailed ways

Embodiment 1, a kind of high pressure penetration test sealing method, adopts the described sealing method, comprises the following steps:

Step 1: Return all push plates of the instrument to their original positions;

Step 2: Glue a rubber sheet around the inlet hole of the water inlet push plate and around the outlet hole of the water outlet plate, place a rubber sheet inside the test chamber, and the rubber sheet covers the front, lower and rear sides of the instrument ( Except for the water inlet surface, water outlet surface and top), the specific size and model of the rubber sheet is determined by the calculated peak shear strength and the allowable thickness of the rubber sheet;

Step 3: Put the customized water bag, place the geotextile and the rubber sheet on the water inlet side of the bag in order, and place the rubber sheet on the water outlet side;

Step 4: Fill the test soil sample from the top of the water bag to the water bag, and each layer of rock and soil material is layered and compacted;

Step 5: Cover the top of the filled water bladder with a layer of rubber sheet;

Step 6: Add a whole sealing strip to the sealing groove reserved at the top of the instrument, connect the two ends of the sealing strip, and fix it with glue;

Step 7: Cover the top of the instrument with the upper cover of the instrument, fix it with a hydraulic nut and apply a certain pressure. The pressure depends on the test conditions and the target stress level. Generally, the hydraulic nut can meet the requirements between the upper cover and the upper cover by adding 10~20Mpa oil pressure. The strength requirements of the connection of the instrument, and at the same time, the sealing strip is deformed and flattened under the action of high pressure and the middle gap is blocked to meet the test sealing requirements;

Step 8: Give a certain initial thrust to the push plates in each direction, so that the soil sample, water bladder, rubber plate and push plate/side wall in the test cavity are in close contact;

Step 9: Pass water to the instrument, and then perform the corresponding penetration test after saturation.

The sealing device used in the above method is suitable for a large three-way loading permeameter, the main body of the large three-way loading permeameter is provided with an upper cover; the large three-way loading permeameter is provided with a push plate that directly acts on the soil. , is characterized in that, there is a water bag 2 for wrapping the soil sample, and the inner side of the outer cavity of the water bag 2 (except the water inlet and outlet surfaces) is affixed with a layer of rubber sheet 1 of a certain thickness; it can prevent water from entering the water bag. into the rear cavity of the water inlet push plate 6 from the outside. In addition, during the pressurization process, the soil sample, the water bladder and the rubber sheet are in close contact, and the soil particles on the edge are embedded in the rubber sheet through the water bladder. , on the other hand, it can reduce the pore channels on the side wall and reduce the side wall effect.

The water inlet surface 3 is the surface inlet, and the water inlet push plate 6 outside the water inlet is provided with water inlet holes 5, and a layer of back-shaped rubber plate 7 with a certain thickness is glued according to the distribution shape of the water inlet holes 5. Corresponding holes are also opened on the water bladder 2 for water intake. A layer of geotextile 8 is attached to the water bladder 2 to prevent soil particles from blocking the water inlet during the pressurization process, and a perforated rubber sheet is clamped on the inner side of the geotextile 8, so that after axial compression, the water bladder And the geotextile will be fixed between the two rubber sheets to prevent the water bladder from moving and deforming greatly during the compression process to form additional pore channels. A whole sealing strip 11 is added to the sealing groove reserved at the top of the instrument, and the two ends of the sealing strip are connected to each other and fixed with glue. The water outlet plate 10 on the water outlet surface 4 is provided with water outlet holes 9 .

Claims (5)

1. A sealing method suitable for a large three-way loading permeameter is characterized by comprising the following steps:

the method comprises the following steps: restoring all push plates of the instrument to the initial position;

step two: a ring-shaped rubber plate is adhered around the water inlet hole of the water inlet push plate and around the water outlet hole of the water outlet plate, a rubber plate is arranged in the test cavity and covers the front surface, the lower surface and the rear surface of the instrument, and the specific size and model of the rubber plate are determined by the calculated peak shear strength and the thickness of the rubber plate allowed by the instrument;

step three: placing a customized water bag, sequentially placing geotextile and a clip-shaped rubber plate on one side of a water inlet surface in the bag body in sequence, and placing the clip-shaped rubber plate on one side of a water outlet surface;

step four: filling the proportioned test soil sample into the water bag from the top of the water bag, and compacting each layer of rock soil material layer by layer;

step five: covering a layer of rubber plate on the top of the filled water bag;

step six: adding a whole sealing strip in a sealing groove reserved at the top of the instrument, connecting interfaces at two ends of the sealing strip, and fixing the sealing strip by using glue;

step seven: the top of the instrument is covered with an upper cover of the instrument, the upper cover is fixed by a hydraulic nut, certain pressure is applied, the pressure depends on the test working condition and the target stress level, the hydraulic nut meets the strength requirement of the joint of the upper cover and the instrument by adding 10-20 Mpa of oil pressure, and meanwhile, the sealing strip deforms and flattens under the action of high pressure and blocks a middle gap to meet the test sealing requirement;

step eight: giving a certain initial thrust to the push plate in each direction to ensure that the soil sample, the water bag, the rubber plate and the push plate/side wall in the test cavity are in close contact;

step nine: introducing water into the instrument, and performing a corresponding penetration test after saturation;

the main body of the large three-way loading permeameter is provided with an upper cover; the large three-way loading permeameter is provided with a push plate directly acting on a soil body and a water bag used for wrapping a soil sample, the inner side of a cavity outside the water bag is adhered with a layer of rectangular rubber plate with a certain thickness, and the thickness of the rectangular rubber plate suitable for the sealing device is 6 mm; a layer of square-shaped rubber plate with certain thickness is adhered outside the water inlet of the water inlet surface of the water bag according to the distribution shape of the water inlet holes, and the thickness of the square-shaped rubber plate suitable for the sealing device is 6 mm; a layer of clip-shaped rubber plate with certain thickness is adhered on the water outlet surface of the water bag according to the distribution shape of the water outlet holes; the inner sides of the water bag, which pass in and out of the water surface, are clamped with perforated rubber plates with certain thickness, and the thickness range of the perforated rubber plates suitable for the sealing device is 10-20 mm; a circle of groove is formed in a top working platform of the large three-way loading permeameter main body, and a sealing strip is added in the middle of the groove.

2. The sealing method for the large three-way loading permeameter according to claim 1, wherein the water bag is shaped and sized according to the size of a test cavity of a specific instrument and used for wrapping a soil sample, the water bag is made of TPU polyurethane soft body and used for storing water and oil, and the material is thickened and has certain strength and elasticity; the top opening of the water bag is used for filling soil samples, and corresponding openings are reserved for water inlet and outlet according to the distribution and shape of the water inlet and the water outlet.

3. The sealing method for the large three-way loading permeameter according to claim 1, wherein the water inlet surface is a surface water inlet, a layer of rectangular rubber plate with a certain thickness is adhered outside the water inlet according to the distribution shape of the water inlet holes, and corresponding holes are opened on the water bag for water inlet; the water bag is internally provided with a layer of geotextile to prevent soil body particles from blocking a water inlet in the pressurizing process, and the inner side of the geotextile is clamped with a perforated rubber plate, so that the water bag and the geotextile can be fixed between the two rubber plates after axial pressurizing, and the water bag is prevented from moving and deforming greatly to form an additional pore channel in the compressing process.

4. The method as claimed in claim 1, wherein the outlet surface is formed by attaching a rubber sheet having a certain thickness to the outlet plate according to the distribution of the outlet holes, and the water bladder is provided with corresponding holes for discharging water and is provided with an opening rubber sheet on the inner side.

5. The sealing method for the large three-way loading permeameter according to any one of claims 1 to 4, wherein the sealing strip between the upper cover and the lower instrument body is arranged in a manner that: a circle of groove is formed in a top working platform of the lower instrument main body, a sealing strip is added in the middle of the groove, the sealing strip is made of circular rubber sealing strips, the diameter of each sealing strip is matched with the width of the groove and is larger than the depth of the groove, and the sealing strips have good elasticity; at the interface, the two ends of the sealing strip are both provided with a certain length, the sealing strip is half-cut by taking the transverse axis as a boundary, an upper half is arranged at one side of the sealing strip, and a lower half is arranged at one end of the sealing strip, and the sealing strip is fixed together by using glue.

Images